The present invention relates to a video tape recording apparatus using an Hadamard transformation system for recording and reproducing a video signal.
In a recently developed video tape recording apparatus a video signal is distributed to a plurality of channels, and the thus distributed video signals are recorded and reproduced with a plurality of fixed type magnetic heads. This apparatus involves the so-called Hadamard tranformation system.
In such video tape recording apparatus, however, in order to obtain an Hadamard transformation signal, an input information is converted into a time series signal of n phasees, so that the input information is usually sampled by some common means.
Further, in recording and reproduction, it is not only necessary to record and reproduce an Hadamard transformation signal but also necessary to record and reproduce a sampling signal with an independent channel or by multiplexing or the like.
In recording and reproducing a sampling signal, however, it is difficult to precisely transmit a phase information from the recording system to the reproducing system if for example, an FM modulation means is used, the phase of a demodulated sampling signal becomes unstable relative to the Hadamard transformation signal after reproduction owing to phase distortion or the like of the FM transmission system.
Therefore, if a sampling signal having such an unstable phase is used as a sampling signal during Hadamard inverse transformation, the reproduced picture image deteriorates considerably.
Moreover, in recording and reproducing apparatus using a fixed-type multi-channel head, time-base fluctuation or, a time jitter and drift in a reproduced signal between channels may be caused by positioning errors of each head and unevenness in the running of the tape.
In order to avoid this problem, a time-base correction signal is generally inserted into horizontal blanking phase portion of a transformed signal and recorded at the time of recording or the like. During reproduction, the recorded time-base correction signal is separated from the transformed signal and the separated signal is used as a signal for detecting time-base fluctuation so as to correct the time-base fluctuations.
The time-base correction is carried out over the whole channel signal and it is also necessary to produce coincidence with the time-base over the whole channel signal, but in practice, the detection of a time delay of a correction loop and time-base fluctuation of the time-base correction device is carried out by a sampling means every period of a horizontal signal, so that information of the time-base fluctuation at the portion other than the sampling point is lacking. For this reason, it is very difficult to completely correct time-base fluctuations. Accordingly, the component which is impossible to be completely correct remains as a residual jitter, and the jitter-drift component remains as part of a reproduced channel signal.
Therefore, the synchronizing signal is separated from the output signal of the time-base corrector independently coupled to each channel at the time of reproduction, the separated synchronizing signal reproduces the signal transformed by Hadamard transformation or time division to as the original video signal by inverse transformation, and the reproduced video signal is coupled to the separated synchronizing signal.
The residual jitter contained in each channel is dispersed and averaged into the whole video signal in an inverse transformer, and in practice, there a difference between the synchronizing residual jitter of one channel and the residual jitter of the reproduced video signal is produced.
In this case, apparent resolution is inadequate because distortion is produced on a monitor screen or the signal is finely modulated on the screen by a difference of residual jitters.